Arjunic acid (2±,32,19±-tri-hydroxy-olea-12-en-28-oic acid) (1) is a triterpenoid compound which exists widely in natural plants in the form of free acid or aglycone for triterpenoid saponins, it has been isolated and identified from various plant species.
The bark of arjun tree Terminalia arjuna has been extensively used in Indian Ayurvedic system of medicine, especially as a cardiac tonic. Vagbhatta mentioned the use of Terminalia arjuna for treating heart diseases about 1200 years ago [L. C. Vaidya, 1963 commentaries on Vagbhatta in “Asttong Hridyam” Motilal Banarsi Das, Varanasi, first edition: 414]. A decoction of its bark with cane sugar and boiled cows milk is highly recommended for endocarditis, pericarditis and angina (Kumar D S and Prabhakar Y S, J. Ethanopharmacology, 1987, 20, 173.). The bark is also prescribed in biliousness and sores and as antidote to poison and it is believed to have an ability to cure hepatic congenital, veneral and viral disease.
Habit: Terminalia arjuna tree is distributed throughout the greater part of India, Burma, and Sri Lanka, wherever plenty of water is available. It is practically found in sub-Himalayan tracks of Uttar Pradesh, South Bihar, Madhya Pradesh and Deccan regions. The trees are also being grown in the road side of big cities as an ornamental tree and they grow well whenever there is collection or flow of water in the neighborhood.
Chemical investigation: Significant work on the chemical investigation of different parts of Terminalia arjuna resulted in the isolation and characterization of number of compounds as given below in Table-1
TABLE 1Phytochemical constituentsof various parts of Terminallia arjunaPartsChemical constituentsStem barkAlkaloids, Tannins, Sugars, Coloring matter,2-Sitosterol, Ellagic acid, CaO, MgO, Al2O3, Arjunolicacid, Arjunic acid (arjunin), Friedlin, Arjunentin,Leucocyanidin, Adrjungenin, Arjunoglucoside-I,Arjunoglucoside-II, Arjunoglucoside-III, Arjunolitin,Arjunolone, Oxalic acid, (+)Catechol, Baicalein,Luteolin, Terminic acid, Flavonoids,Root barkEllagic acid, Gallic acid, Arjunatin, leucocyanidin,Arjunoglucoside-I, Arjunoside-II, Arjunoside-III,Arjunoside-IV, Terminic acid, 2-hydroxyhexadecanoicacid.FruitsTannin, Ellagic acid, Gallic acid, Xylan, Mannitol,KCl, Sitosterol, Sitosterolglucoside, Afxormosin,Quercitin-7-Orhamnoside, Arjunic acid, Arjunone,Cerasidin, Methyl-oleanorate, Hentriacontone,Arachidic sterate, Myristyloleate, Triterpeneglycoside(Terminolitin), Hentriacontane.
Biological activities: Pettit et al have examined, the cancer cell growth inhibitory constituents residing in the bark, stem, leaves of the Marutious medicinal plant T. arjuna by means of bioassay-guided separation method. The cancer line active components were found to be gallic acid, ethyl gallate flavone, leutonolin. Luteolin has a well established record of inhibiting various cancer cell lines and may account for the most of the rationale underlying the use of T. arjuna in traditional cancer treatment. Luteolin was also found to exhibit specific activity against the pathogenic bacteria Neisseria gonorrhoeae [G R Pettit, M S Hoard, D L Doubek, J M Schmidt, R K Pettit, L P Tackett, J C Chapuis, 1996, J Ethnopharmacology, 53, 57]. Kaur et al reported the antimutagenic potential of a fraction isolated from T. arjuna, evaluated in TA98 and TA100 strains of salmonella typhimurium against direct and indirect acting mutagens. The fraction was quit effective against 59-dependent 2AF while it showed moderate effect against NPD. The fraction was finally identified as Ellagic acid (S J Kaur, I S Grover, S Kumar, 1997, Ind J Exp Biol, 35, 478). Kandil et al have isolated a new ellagitanin named, Arjunin along with four known tannins and two phenolic acids from T. arjuna. The biological activity examination of the ethnolic extract of the leaves of T. arjuna and isolated compound Arjunin showed that they have moderate cytotoxic activity against BT-20 human breast carcinoma cells. The IC50 of the extract and the compound Arjunin were 2.5 and 6.5 mg/ml, respectively. The growth inhibition effect of compound Arjunin was higher than that of the extract (F E Kandil, I N Mahmood, 1998, Phytochemistry, 47, 1567.)
Chaturvedi et al. reported that the alcoholic extract of T. arjuna has statistically significant hypocholesterolemic, hypolipidemic, anticoagulant and fibrinolytic effect on hypercholesterolemic rabbits. It also shows no definite action on the serum phospholipids. The alcoholic extract has no protective action against isoprenaline induced experimental myocardial injury. Pharmacological investigations show “arjuna” has cardiotonic property in animals. They concluded that it may be safely used for the prevention and treatment of the patients of ischaemic heart diseases [G. N. Chaturvedi. 1973. Studies on ischaemic—heart diseases and its management by indegenious drugs, Ph.D. Thesis, Dept. of Kayachikitsa I.M.S., B.H.U., varanasi].
Pathak et al. reported that T. arjuna bark powder in the dose of 20 mg/100 gm body weight shows a significant reduction in plasma cholesterol, plasma catecholamine along with lowering in plasma protein and brain catecholamine in the infarcted rats. Their study suggests the importance of this drug as a possible remedy in myocardial infarction as it was shown to be hypocholesteremic, anticatecholaminic and possibly an inhibitor of catecholamine release from the adrenal glands [S. R. Pathak, R. H. Singh, K. N. Udupa. 1987. Alter. Med. 2: 203].
It was observed that although arjunic acid has been isolated earlier by some other workers, due to the poor yield and tedious column chromatographic separation procedures of the anticancer agent from the bark of T. arjuna this bioactive constituent will become an expensive pharmaceutical compound. This prompted us to develop an inexpensive, easy and economical isolation process for this important anticancer agent so that it can be brought within reach of the common masses.
On going through the literature, it was observed that arjunic acid was isolated from the bark of T. arjuna in −0.025% yield (Row L R et al, 1970, Ind J Chem, 8, 716-721). This process involved successive extraction of powdered T. arjuna bark with petroleum ether, ether and ethanol in a large Soxhlet extractor. The ether extract during removal of solvent yielded a crystalline powder, which was dissolved in acetic acid and filtered. The filtrate on dilution with water gave a solid, which on crystallization with MeOH afforded arjunic acid in −0.025% yield.
The method described above suffers from a number of disadvantages. The biggest disadvantage is the low yield of arjunic acid. The second disadvantage of the above process is that the total solid is being dissolved in acetic acid. Since arjunic acid itself is an acid, hence it would have not been dissolved completely in acetic acid, which may be one of the reasons for the poor yield of arjunic acid in this process.
In 1986 Honda et al (Bull. Chem. Soc. Japan, 49, 3213-3218) reported isolation of arjunic acid from the bark of T. arjuna in 0.02% yield. The process involved cold extraction of powdered T. arjuna bark with MeOH followed by addition of lead acetate resulting in the precipitation of the material followed by filtration. To the filtrate further water was added to obtain more precipitate. The combined precipitates were further subjected to column chromatographic separation, which yielded arjunic acid in ˜0.020% yield.
The method described above suffers from a number of disadvantages. The biggest disadvantage is the low yield of anticancer agent arjunic acid. The second disadvantage of the above process is that it utilizes a tedious column chromatographic method for separation of arjunic acid.
In 1982 Anjaneyulu and Rama Prasad (Ind J Chem, 21B, 530-533) reported the isolation of arjunic acid from the root bark of T. arjuna in ˜0.015% yield. The isolation process involved successive extraction of powdered root bark of T. arjuna with n-hexane, chloroform, ethanol and EtOAc. The concentrated chloroform extract after maceration with hot ether gave arjunic acid in 0.015% yield.
The method described above suffers from a number of disadvantages. The biggest disadvantage is the poor yield of arjunic acid. The second disadvantage of the above process is that arjunic acid is being isolated from CHCl3 extract of T. arjuna root bark, this may be the reason for poor yield of arjunic acid as it is not highly soluble in CHCl3.
The method described above suffers from a number of disadvantages. The biggest disadvantage is the low yield of anticancer agent arjunic acid. The second disadvantage of the above process is that it utilizes a tedious column chromatographic method for the separation of arjunic acid.